Abstract
Purpose: :
Accommodation and convergence are closely related. We explore optical explanations of that relationship by analyzing the changes in the on–axis ocular aberrations during accommodation with and without convergence.
Methods: :
We use a modified irx3 aberrometer (Imagine Eyes) to obtain ocular aberrations in 15 visually–normal (ages from 19 to 39) while their accommodation was stimulated with a target of vergence varying from 0 (far point) to 10 D in steps of 0.5 D. Aberrations were measured under monocular conditions with a fixed nasal convergence of 0 (non convergence), 5, 10 degrees. The untrained subjects ran several trials prior to the 3 accommodation measured obtained for each degree of convergence. Zernike coefficients up to eight–order were computed for a natural pupil size (taking into account accommodative miosis). Then accommodation and its amplitude were calculated objectively from wavefront outcomes using different metrics which took into account the change of spherical aberration.
Results: :
An increase of accommodation response up to 2 D after converging was found for most of the non trained subjects. However, with training we obtained a mean increase of 0.3 D (non significant) in the amplitude of accommodation after convergence. Nevertheless, in some subjects, at the higher accommodation states, we found systematic changes in aberrations for different convergences decreasing the accommodation lag up to 1 D. Those changes were correlated to changes in pupil diameter between different convergences conditions.
Conclusions: :
In average, we did not find significant changes in the optics of the eye in our group of study after nasal convergence for 5 and 10 degrees. However, there were in general small (non significant) changes in ocular aberrations after convergence and individual systematic changes on aberrations which modified their accommodation response.
Keywords: optical properties